diff --git a/gtfs-realtime/spec/en/reference.md b/gtfs-realtime/spec/en/reference.md
index 75dfa9d8..086f50c1 100644
--- a/gtfs-realtime/spec/en/reference.md
+++ b/gtfs-realtime/spec/en/reference.md
@@ -634,10 +634,10 @@ A `Modification` message replaces a span of n stop times (`num_stops_replaced`)
The sequence of `new_stops` may be of arbitrary length. For example, 3 stops could be replaced by 2, 4, or 0 stops as the situation may require.
-
+
An example showing the effect of a modification on a particular trip. This modification may also be applied to several other trips.
-
+
Propagated detour delays affect all stops following the end of a modification. If a trip has multiple modifications, the delays are accumulated.
@@ -656,7 +656,7 @@ Each `ReplacementStop` message acts as a template for generating a new stop time
The `arrival_time` is calculated from a reference stop in the original trip, plus the offset in `travel_time_to_stop`. The `departure_time` always equals the `arrival_time`.
The optional fields of [`stop_times.txt`](https://github.com/google/transit/blob/master/gtfs/spec/en/reference.md#stop_timestxt) in the GTFS-Static specification are all set to their default values.
-
+
If a modification affects the first stop of the trip, that stop also serves as the reference stop of the modification.
**Fields**